Hi Folks, very new here, but want a few more opinions on my plans to add an underseat subwoofer to my 2009 Volvo C30.

I'm looking to add in this 150W subwoofer and also add bluetooth seeing as it doesn't have it. The new wiring layout is as follows:

Volvo Head Unit --> Bluetooth Harness connector ( ) --> Spliced RCA Converter (https://www.ebay.co.uk/itm/Connects2-CTLOC15-2-Channel-Speaker-RCA-Phono-Adaptor-Hi-Low-/381630597901?hash=item58daf4cb0d) --> Subwoofer (connected by new RCA) -> Factory speakers (connected to the converter)

As for power for the Sub, it is 150W running at 12V so P = IV; I = 12.5A. So it will need 12.5A

The passenger fuse box ranges from fuse 43 to 86. My C30 has no sunroof, no heated seats and no powered seats. Thats a free (20A + 15A + 15A +25A + 25A) = 100A (I know it doesn't work this way, but it just means that the fusebox was designed to handle a lot more than an extra 12.5A.

I'll probably use number 81 as its a 20A not in use and put a 15A splice on it for the sub.

Then just wire it in and hide the wires and hope it works. Am I missing some vital info?

 

I would not go there with changing anything to do with the radio in this car. There are many posts (including a previous one of mine) that warn of the catastrophic AIR BAG MODULE FAILURE SRS-CFFF issues that can be traced to wiring changes with the radio, amp, or speakers. This issue then requires replacing that module at a dealer cost of $1200!!!!!.